This is not directly my problem but its my friend's problem. He said that when he starts his computer, it says to replace cmos battery, and it wont start. I think thats a real poor description, but he doesn't know about computers much (not that I know alot). Anyway, I told him to go to CMOS and load setup defaults (I told him to go to fail-safe, but he said he doesnt have one) so it loaded, restarted. Then it says.. Setup Defaults Loaded.. CMOS Battery Failed.. =\ What does that mean? I'm not even sure if its software problem or hardware problem...

When you unplug your computer there is no power flowing throught the motherboard anymore. So you need something to power up the BIOS chip so it would store the settings. There is a battery size a little smaller than a quarter, and diameter about 2cm. You have to go get a new one and then replace the old one.

CMOS is Complementary Metal Oxide Semiconductor.It is one type of chip that holds data without external power.In your computer there is a BIOS settings and these settings are saved after changes only because of this CMOS chip.This chip is on motherboard and it can replace easily.CMOS has it's own memory.